FCC counter-current regenerator with a regenerator riser

ABSTRACT

A counter-current catalyst regenerator with at least two stages of counter-current contact along with a regenerator riser is proposed. Each stage may comprise a permeable barrier that allows upward passage of oxygen-containing gas and downward passage of coked catalyst into each stage, but inhibits upward movement of catalyst to mitigate back mixing and approximate true counter-current contact and efficient combustion of coke from catalyst. The regenerator riser may provide a passage to transport the catalyst and may serve as a secondary stage for coke combustion to provide the regenerated catalyst.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application No.62/439,358 filed Dec. 27, 2016, the contents of which cited applicationare hereby incorporated by reference in its entirety.

FIELD

The field of the subject matter relates to catalyst regeneration influidized catalytic cracking units, and more particularly relates to acounter-current catalyst regenerator with a regenerator riser.

BACKGROUND

Fluid catalytic cracking (FCC) is a hydrocarbon conversion processaccomplished by contacting hydrocarbons in a fluidized reaction zonewith a catalyst. As the cracking reaction proceeds substantial amountsof highly carbonaceous material referred to as coke are deposited on thecatalyst. A high temperature regeneration operation within aregeneration zone combusts coke from the catalyst. Coke-containingcatalyst, referred to herein as coked catalyst, is continually removedfrom a reactor and replaced by essentially coke-free catalyst from aregenerator.

In the regenerator, the coke is burned from the catalyst withoxygen-containing gas, usually air. Flue gas formed by burning coke inthe regenerator may be treated for removal of particulates and heatrecovery by oxidation of carbon monoxide. The main goal of theregenerator is to burn the coke off the catalyst, so high coke burnefficiency i.e. combusting most of the coke in shorter residence time,is preferred because it will reduce the equipment size, operational costand emission levels.

After burn is a phenomenon that occurs when hot flue gas that has beenseparated from regenerated catalyst contains carbon monoxide thatcombusts to carbon dioxide in a dilute phase of catalyst containingoxygen. Incomplete combustion of coke to carbon dioxide can result frominsufficient oxygen in the combustion gas, poor fluidization or aerationof the coked catalyst in the regenerator vessel or poor distribution ofcoked catalyst in the regenerator vessel. The heat from after burn canbe detrimental to regenerator equipment.

Because FCC units that process heavy residue feed generate more heatthan is needed to vaporize feed and to promote the cracking reaction itis desirable to control the regeneration temperature and heat release tothe reactor. The two most common ways to control regenerationtemperature are to control the ratio of carbon dioxide to carbonmonoxide and to use catalyst coolers to generate steam and cool thecatalyst. It is most economical to run at the highest carbon monoxideconcentration possible in the flue gas to recovery heat from the fluegas in a downstream CO boiler. However, operating at a low CO₂-to-COratio carries the risk of after burn and uncombusted coke left oncatalyst.

Several types of catalyst regenerators are in use today. A conventionalbubbling bed regenerator typically has just one section in which air isbubbled through a dense catalyst bed. Coked catalyst is added, andregenerated catalyst is withdrawn from the same dense catalyst bed. Inorder to maximize the regenerated catalyst activity at a given make upcatalyst rate, the carbon on catalyst must be reduced to a minimum.

Most modern residue fluid cracking units use a two-stage bubbling bedregenerator to finish the catalyst clean up and reduce the carbon oncatalyst to a minimum. Two-stage bubbling beds have two sections. Cokedcatalyst is added to a dense bed in an upper, first section and ispartially regenerated with air in flue gas from a second stage. Thepartially regenerated catalyst is transported to a dense bed in a lower,second section and completely regenerated with air. The completelyregenerated catalyst is withdrawn from the second section. The secondstage is generally operated in complete combustion where all carbonmonoxide is converted to carbon dioxide and an excess of oxygen ispresent in the flue gas.

In a one or two-stage fluidized bubbling bed regenerator, catalystlifted upwardly by air distributed into the regenerator fallsnon-uniformly in a phenomenon called back mixing. In bubbling beds, thecatalyst phase is back mixed from top to bottom while the gas phase isnearly plug flow with a high oxygen concentration at the bottom and lowoxygen concentration at the top. Back mixing causes the residence timeto increase and the combustion rate to be non-uniform which can generatehot spots, increase catalyst deactivation and reduce combustionefficiency. Back mixing also lowers the catalyst bed density therebyincreasing the equipment size.

FCC regenerators are large in size and costly to build. They are largebecause of the requirement to stage air supply to burn large amounts ofcoke on spent catalyst. Without staging the combustion of coke is likelyto generate enough heat to destroy the zeolite framework of the catalystand render it inactive.

Therefore, there is a need for improved processes and apparatuses forefficiently regenerating catalyst while preventing after burn and backmixing. There is a need for a process and an apparatus to better controlcoke and oxygen concentration and temperature profiles in a regeneratorwhich promotes more efficient combustion of coke from catalyst. Further,there is a need for an apparatus that improves FCC regeneratorefficiency and reduces vessel size.

SUMMARY

The disclosed subject matter is a counter-current catalyst regeneratorwith at least two stages of counter-current contact along with aregenerator riser. Each stage may comprise a permeable barrier thatallows upward passage of oxygen-containing gas and downward passage ofcoked catalyst into each stage, but inhibits upward movement of catalystto mitigate back mixing and approximate true counter-current contact andefficient combustion of coke from catalyst. The regenerator riser mayprovide a passage to transport the catalyst and/or may serve as asecondary stage for coke combustion to provide the regenerated catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, elevational view of an FCC unit incorporating thepresent subject matter according to an embodiment.

FIG. 2 is a schematic, elevational view of an FCC unit incorporating thepresent subject matter according to another embodiment.

FIG. 3 is a schematic, elevational view of an FCC unit incorporating thepresent subject matter according to yet another embodiment.

DETAILED DESCRIPTION

A new regenerator is proposed in which catalyst and gas flowcounter-currently to each other in multiple stages and is provided withinternal or external regenerator riser to facilitate catalyst transport.A permeable barrier above each stage may facilitate counter-current flowof catalyst by mitigating catalyst back mixing. The permeable barriercan also have a structure that facilitates effective mixing betweencatalyst and combustion gas. Each stage may also include a section ofopen volume between adjacent permeable barriers. A catalyst flowsdownwardly from a stage through a subjacent permeable barrier andoxygen-containing gas flows upwardly from the stage through superjacentpermeable barrier. One or more stages may be assembled in theregenerator vessel to approach true counter-current flow conditions.Further, the regenerator riser may serve as the last polishing stage ofcatalyst regeneration after the countercurrent regeneration in themultiple stages. Alternatively, the regenerator riser may serve as thefirst stage of the regeneration process.

In the new regenerator, catalyst flow and catalyst residence time aremore uniform. The residence time necessary for the catalyst to achievecomplete coke burn can be accurately controlled and therefore reduced.The thermal deactivation of catalyst due to randomly long residence timecan be avoided. Additionally, the counter-current flow regime generatesa favored concentration profile along the regenerator vessel. At thetop, initial stage, the catalyst has the highest coke concentration butthe combustion gas has a low oxygen concentration, so after burn can beavoided. At the bottom, last stage, the oxygen-containing gas has thehighest oxygen concentration, but the catalyst has the lowest cokeconcentration, so again the after burn can be prevented.

Catalyst density can be increased in the regenerator vessel because thecatalyst downward flow pattern is more uniform. Consequently, for thesame catalyst inventory, the regenerator size can be smaller.Additionally, because the oxygen concentration can be higher where thecoke concentration on catalyst is lower, the overall oxygen-containinggas flow rate can be reduced, so the regenerator size and operation costcan be reduced. Further, by using internal or external risers tofacilitate catalyst transport a shorter regenerator vessel issufficient. In this manner, a spent catalyst standpipe and a regeneratedcatalyst standpipe can be brought closer together and the FCC unit canbecome shorter thus saving capital costs.

Although other uses are contemplated, the process and apparatus may beembodied in an FCC unit. FIG. 1 shows an FCC unit that includes areactor section 10 and a regenerator vessel 50. A regenerated catalystconduit 12 transfers regenerated catalyst from the regenerator vessel 50at a rate regulated by a control valve 14 to a riser 20 of the reactorsection 10. An inert fluidization medium such as steam from a nozzle 16transports regenerated catalyst upwardly through the riser 20 at arelatively high density until a plurality of feed distributor nozzles 18inject hydrocarbon feed perhaps mixed with inert gas such as steamacross the upwardly flowing stream of catalyst particles. The catalystcontacts the hydrocarbon feed cracking it to produce smaller, crackedhydrocarbon products while depositing coke on the catalyst to producecoked catalyst.

A conventional FCC hydrocarbon feedstock and higher boiling hydrocarbonfeedstock are suitable fresh hydrocarbon feed streams. The most commonof such conventional fresh hydrocarbon feedstocks is a “vacuum gas oil”(VGO), which is typically a hydrocarbon material having a boiling rangewith an IBP of no more than about 340° C. (644° F.), a T5 between about340° C. (644° F.) to about 350° C. (662° F.), a T95 between about 555°C. (1031° F.) and about 570° C. (1058° F.) and/or an EP of no more thanabout 640° C. (1184° F.) prepared by vacuum fractionation of atmosphericresidue. Such a fraction is generally low in coke precursors and heavymetal contamination which can serve to contaminate catalyst. Atmosphericresidue is a preferred feedstock boiling with an IBP not more than about340° C. (644° F.), a T5 between about 340° C. (644° F.) and about 360°C. (680° F.) and/or a T95 of between about 700° C. (1292° F.) and about900° C. (1652° F.) obtained from the bottom of an atmospheric crudedistillation column. Atmospheric residue is generally high in cokeprecursors and metal contamination. Other heavy hydrocarbon feedstockswhich may serve as fresh hydrocarbon feed include heavy bottoms fromcrude oil, heavy bitumen crude oil, shale oil, tar sand extract,deasphalted residue, products from coal liquefaction and vacuum reducedcrudes. Fresh hydrocarbon feedstocks also include mixtures of the abovehydrocarbons and the foregoing list is not comprehensive.

The FCC catalyst includes a large pore zeolite, such as a Y-type zeoliteand a matrix material comprising an active alumina material, a bindermaterial, including either silica or alumina, and an inert filler suchas kaolin. In accordance with an exemplary embodiment, suitable FCCcatalyst may include Upgrader from Albemarle Corporation located inBaton Rouge, La. The FCC catalyst may also include 1 to 25 wt % of amedium or smaller pore zeolite catalyst, such as a MFI zeolite,dispersed on a matrix including a binder material such as silica oralumina and an inert filler material such as kaolin.

The resulting mixture of cracked hydrocarbon products and coked catalystcontinues upwardly through the riser 20 to a top at which a plurality ofdisengaging arms 22 tangentially and horizontally discharge the mixtureof gas and catalyst from a top of the riser 20 through ports 24 into adisengaging vessel 26 that effects a rough separation of gases from thecatalyst. A transport conduit 28 carries the hydrocarbon vapors,including stripped hydrocarbons, stripping media and entrained catalystto one or more cyclones 30 in a reactor vessel 32 which separates cokedcatalyst from the hydrocarbon vapor stream. The reactor vessel 32 may atleast partially contain the disengaging vessel 26, and the disengagingvessel 26 is considered part of the reactor vessel 32. A collectionsection 34 in the reactor vessel 32 gathers the separated hydrocarbonvapor streams from the cyclones 30 for passage to an outlet nozzle 36and eventually into a fractionation recovery zone (not shown). Diplegs38 discharge catalyst from the cyclones 30 into a lower portion of thereactor vessel 32, and the catalyst and adsorbed or entrainedhydrocarbons pass into a stripping section 40 of the reactor vessel 32across ports 42 defined in a wall of the disengaging vessel 26. Catalystseparated in the disengaging vessel 26 passes directly into thestripping section 40. The stripping section 40 contains baffles 43, 44or other equipment to promote mixing between a stripping gas and thecatalyst. The stripping gas enters a lower portion of the strippingsection 40 through a conduit to one or more distributors 46. Thestripped, coked catalyst leaves the stripping section 40 of the reactorvessel 32 through a reactor catalyst conduit 48 and passes to theregenerator vessel 50 at a rate regulated by a control valve 52. Thecoked catalyst from the reactor vessel 32 usually contains carbon in anamount of from 0.2 to 2 wt %, which is present in the form of coke.Although coke is primarily composed of carbon, it may contain from 3 to12 wt % hydrogen as well as sulfur and other materials.

The regenerator vessel 50 for combusting coke from catalyst comprises aregeneration section 54 and a separation section 56. Although forexemplary purposes, the diameter of the regeneration section 54 and theseparation section 56 have been shown of about the same diameter,however, in various embodiments, diameter of the regeneration section 54may be different form the diameter of the separation section 56. Theregenerator vessel 50 may include a regenerator riser 102 and one ormore stages for countercurrent regeneration of a catalyst, describedlater in detail. The one or more stages may be present in theregeneration section 54. Each of the one or more stages may comprise apermeable barrier. The reactor catalyst conduit 48 may provide the cokedcatalyst to an inlet 104 in a bottom of a regenerator riser 102. Thecoked catalyst may be propelled upwardly from the bottom of theregenerator riser 102 to a top of the regenerator riser 102 via asecondary stream of gas. In accordance with an exemplary embodiment asshown in the FIG. 1, the regenerator riser 102 may be located and passesthrough inside of the regenerator vessel 50 through the axial centerthereof. The riser regenerator 102 may have a vertical orientationwithin the regenerator vessel 50 and may extend upwardly from the bottomof the regenerator vessel 50. The secondary stream of gas may beintroduced through a secondary gas distributor 110. In some embodiments,the secondary stream of gas may be an oxygen containing gas. Inaccordance with an exemplary embodiment as shown in the FIG. 1, thesecondary stream of gas may be provided by a combustion gas stream inline 62. As shown in FIG. 1, the secondary stream of gas may be providedby the secondary gas distributor 110. In some embodiments, coke may becombusted as the catalyst moves upwardly from the bottom of theregenerator riser to provide a partially regenerated catalyst at the topof the regenerator riser 102.

The catalyst may be discharged from an outlet 114 at the top of theregenerator riser 102. The regenerator riser 102 comprises a disengager112 comprising the outlet 114 for discharging the catalyst. Inembodiment where catalyst is regenerated in the regenerator riser, thedisengager 112 roughly separates the catalyst from a second flue gasgenerated in the regenerator riser. The second flue gas may be the fluegas generated via combustion of coke from the catalyst in theregenerator riser 102. The CO₂-to-CO mole ratio for the second flue gasfrom the regenerator riser may be between about 1 and greater than 0.

Subsequently, the catalyst discharged from the regenerator riser 102 maybe passed downwardly through the one or more stages. Applicants havefound that two stages of countercurrent contact of coked catalyst andoxygen-containing gas provides increased volume reduction over a singlebubbling bed regenerator. Three stages of countercurrent contactprovides increased volume reduction, but the increasing benefit ofvolume reduction begins to incrementally diminish at four and fivestages. More than five stages appears to provide less incrementalbenefit which may not be economically justified. Each of the one or morestages may include a permeable barrier having openings sized to permitthe coked catalyst to pass through downwardly, the permeable barrierextending laterally across the regenerator vessel. In variousembodiments, the one or more stages may be categorized as the firststage 70, one or more intermediate stages 75 and the last stage 78.

In accordance with an exemplary embodiment the one or more stages maycomprise a first stage 70 disposed below the catalyst inlet. The firststage 70 may be defined on an upside by a first permeable barrier 80.The first permeable barrier 80 extends laterally across the regeneratorvessel. In an aspect, the first permeable barrier 80 extends laterallyacross the entire regeneration section 54 of the regenerator vessel 50contiguously with the wall 53 of the regenerator vessel 50. The catalystinlet delivers coked catalyst above the first stage and in an aspect,the first permeable barrier 80.

The first permeable barrier 80 may comprise any structure that allowsupward flow of gas and downward flow of catalyst, but inhibits backmixing or upward flow of catalyst that may be entrained in the gas.Consequently, upward movement of catalyst is prevented above the firststage 70 by the first permeable barrier 80 more so than if the firstpermeable barrier 80 were not present. The first permeable barrier 80may comprise inclined vanes, gratings, structural packing, baffles,including disc and doughnut baffles, chevrons and shed decks, perforatedplates and the like. An intermediate permeable barrier 85 may be spacedbelow the first permeable barrier 80 to define a first section 90between that is devoid of internal structure.

One or more intermediate stages 75 may be disposed below the first stage70. Each stage in the one or more intermediate stages 75 may be definedon an upside by the intermediate permeable barrier 85. The intermediatepermeable barrier 85 extends laterally across the regenerator vessel 50.In an aspect, the intermediate permeable barrier 85 extends laterallyacross the entire regeneration section 54 of the regenerator vessel 50contiguously with the wall 53 of the regenerator vessel 50. Inaccordance with an exemplary embodiment as shown in the FIG. 1, theregeneration section 54 comprises three intermediate stages defined onan upside by the intermediate permeable barriers 85 a, 85 b and 85 c,respectively. The regeneration section also includes a last intermediatebarrier 85 d.

An intermediate permeable barrier 85 b, 85 c, 85 d may be spaced belowan adjacent intermediate permeable barrier 85 a, 85 b, 85 c locatedimmediately above to define an intermediate section 95 there betweenthat is devoid of internal structure. The intermediate section 95 mayextend laterally across the regenerator vessel 50 between two adjacentintermediate permeable barriers 85 a, 85 b, 85 c. Accordingly, thesection formed between two adjacent permeable barriers may extendlaterally across the regenerator vessel 50. The intermediate permeablebarrier 85 may comprise any structure that allows upward flow of gas anddownward flow of catalyst, but inhibits back mixing or upward flow ofcatalyst that may entrain in the combustion gas, similar or the same asthe first permeable barrier 80. It is contemplated that the firstsection 90 and the intermediate section(s) 95 may contain furtherinternal structure to inhibit back mixing of catalyst or facilitatecontact between catalyst and gas.

The last stage 78 may be disposed below the one or more intermediatestages. In accordance with an exemplary embodiment as shown in the FIG.1, the last stage 78 is the fifth stage and may be disposed below afourth stage 75 or a third intermediate permeable barrier 85 c. The laststage 78 may be defined on an upside by a last intermediate permeablebarrier 85 d. The last intermediate permeable barrier 85 d may extendlaterally across the regenerator vessel 50. In an aspect, the lastintermediate permeable barrier 85 d extends laterally across the entireregeneration section 54 of the regenerator vessel 50 contiguously withthe wall 53 of the regenerator vessel 50. The last intermediatepermeable barrier 85 d may be spaced apart below the intermediatepermeable barrier 85 c of a last intermediate stage 75 to define thelast intermediate section 95 therebetween that is devoid of internalstructure. The last intermediate permeable barrier 85 may comprise anystructure that allows upward flow of gas and downward flow of catalyst,but inhibits back mixing or upward flow of catalyst that may entrain inthe combustion gas, similar or the same as the first permeable barrier80.

In an embodiment, only five stages of counter-current contact areprovided. More or less stages may be provided, but volume reductiondiminishes after four or five stages of counter-current contact betweencoked catalyst and oxygen-containing gas.

A last permeable barrier 100 may extend laterally across the regeneratorvessel 50. In an aspect, the last permeable barrier 100 extendslaterally across the entire regeneration section 54 of the regeneratorvessel 50 contiguously with the wall 53 of the regenerator vessel 50. Inaccordance with an exemplary embodiment as shown in FIG. 1 includingfive stages, the last permeable barrier 100 may be spaced apart belowthe last intermediate permeable barrier 85 d to define a last section 98therebetween that is devoid of internal structure. The last section 98may extend laterally across the regenerator vessel 50 between the lastintermediate permeable barrier 85 d and the last permeable barrier 100.The last permeable barrier 100 may comprise any structure that allowsupward flow of gas and downward flow of catalyst, but inhibits backmixing or upward flow of catalyst that may entrain in the combustiongas, similar or the same as the first permeable barrier 80. It iscontemplated that the last section 98 may contain further internalstructure to inhibit back mixing of catalyst or facilitate contactbetween catalyst and gas.

Each of the permeable barriers may be supported on the wall 53 of theregeneration section 54 with additional support as necessary. The heightof the spacing of sections 90, 95 and 98 between permeable barriers 80,85 and 100 may be the same as the height of the permeable barrier. In anaspect, the height of the spacing of sections 90, 95 and 98 may be aboutone-half to about three-fourths the height of the permeable barrierabove it. Moreover, the height of the spacing of sections 90, 95 and 98between permeable barriers 80, 85 and 100 may be one-sixth tothree-eighths of the diameter of the regeneration section 54. Moreover,the height of the permeable barrier may be as much as one-third of thediameter of the regeneration section 54.

A primary stream of oxygen-containing gas, typically air, is passedupwardly through the one or more stages in counter-current contact withthe coked catalyst from the catalyst inlet to combust coke from thecoked catalyst to provide a regenerated catalyst and a first flue gas.Accordingly, the first flue gas may be the flue gas generated viacombustion of coke from the coked catalyst in the one or more stages. Inaccordance with an exemplary embodiment as shown in the FIG. 1, theprimary stream of oxygen containing gas may be provided from acombustion gas in line 63. In accordance with an exemplary embodiment asshown in the FIG. 1, the primary stream of oxygen containing gas may bedelivered by a primary combustion gas distributor 64 through anoxygen-containing gas inlets 65 to the regeneration section 54 in theregenerator vessel 50. The oxygen-containing gas counter-currentlycontacts coked catalyst in the lower, regeneration section 54 under flowconditions which will include a superficial gas velocity of 0.3 m/s (1ft/s) to 2.2 m/s (7 ft/s) and a catalyst density of from about 320 kg/m3(20 lb/ft³) to about 750 kg/m³ (35 lb/ft³) in the counter-currentcontacting stages 70, 75 and 78. The catalyst density will be about 16kg/m³ (1 lb/ft³) to about 80 kg/m³ (5 lb/ft³) in the dilute phase in theseparation section 56. The oxygen in the combustion gas contacts thecoked catalyst and combusts carbonaceous deposits from the catalyst.Oxygen may be added in proportion to combust coke from the cokedcatalyst in a partial burn or full burn mode to generate the first fluegas and regenerated catalyst. In accordance with an exemplary embodimentas shown in the FIG. 1, one or more vent tubes (not shown) may bepresent for passage of the first flue gas from the regeneration section54 to the separation section 56.

The process of combusting coke from coked catalyst begins with passing afirst stream of coked catalyst downwardly from the catalyst inletthrough the first stage 70. In one example, a catalyst distributor mayroughly distribute coked catalyst through its nozzles along the top ofthe first permeable barrier 80. The first stream of coked catalyst maypass through an opening or openings in the first permeable barrier 80into the first stage 70. A first stream of oxygen-containing gas iscompelled upwardly through the first stage 70 in counter-current contactwith the first stream of coked catalyst at high temperature to combustcoke deposits from the first stream of coked catalyst. Thecounter-current contacting occurs in the first section 90. The firststream of oxygen-containing gas has been in contact with all of thelower stages and has a large concentration of flue gas and a smallerconcentration of oxygen. However, the first stream of coked catalyst inthe first stage has the highest concentration of coke deposits. Hence,the high concentration of coke deposits provides a large differentialdriving force which readily combusts coke in the low concentration ofoxygen in the first stage 70. Additionally, in the first stage 70 hotflue gas highly concentrated in oxygen may strip adsorbed hydrocarbonsfrom the coked catalyst due to less availability of oxygen. Strippingremoves adsorbed coke and combustion causes some of the coke deposits tocombust from the catalyst to produce flue gas and provides a secondstream of coked catalyst including at least partially regeneratedcatalyst with a lower concentration of coke and a stream of flue gaswith a low concentration of oxygen.

The stream of flue gas is passed upwardly from the first stage 70through the first permeable barrier 80. However, the first permeablebarrier 80 inhibits upward movement of the coked catalyst in the firststage, causing it to lose upward momentum and fall downwardly in thefirst stage 70. Consequently, the second stream of coked catalyst movesdownwardly through an opening or openings in the second permeablebarrier from the first stage 70 into the first intermediate stage 75below the first stage in opposite direction to the upwardly flowingsecond stream of oxygen-containing gas. In an aspect, all of the gasfrom the first stage 70 passes upwardly through an opening or openingsin the first permeable barrier 80, and at least 99 wt % of the catalystfrom the first stage passes downwardly through an opening or openings inthe first intermediate permeable barrier 85 a located immediately belowthe first permeable barrier 80.

Similarly, an intermediate stream of oxygen-containing gas is passedupwardly through the one or more intermediate stages 75 incounter-current contact with the intermediate stream of coked catalystin each of the one or more intermediate stages 75. For example, a secondstream of oxygen-containing gas is passed upwardly through the firstintermediate stage 75 in counter-current contact with the second streamof coked catalyst descending from the first stage 70 to combust cokefrom the second stream of coked catalyst. A stream of oxygen-containinggas in a lower intermediate stage 75 has a larger oxygen concentrationthan a stream of oxygen-containing gas in an upper intermediate stage75, but the coke concentration on catalyst in the lower intermediatestage is lower than the coke concentration of coked catalyst in theupper intermediate stage. Hence, a differential driving force ismaintained to drive combustion of the smaller concentration of cokedeposits in the second stream of catalyst. The counter-currentcontacting may occur in the intermediate section 95 in the intermediatestage 75.

The counter-current contacting of the intermediate stream of cokedcatalyst and the intermediate stream of oxygen-containing gas combustscoke from the catalyst to produce a stream of coked catalyst includingregenerated catalyst with a reduced concentration of coke deposits and astream of oxygen-containing gas including flue gas. The stream of cokedcatalyst in the intermediate stage 75 is inhibited from upward movementby the intermediate permeable barrier 85 and loses its momentum.Consequently, the stream of coked catalyst provided by the intermediatestage 75 moves downwardly through an opening or openings in theintermediate permeable barrier 85 of an upper intermediate stage 75 inopposite direction to the upwardly flowing stream of oxygen-containinggas produced in a lower intermediate stage 75. In an aspect, all of thegas from the intermediate stage 75 passes upwardly through an opening oropenings in the intermediate permeable barrier 85 located immediatelyabove the lower intermediate permeable barrier 85, and at least 99 wt %of the catalyst from the intermediate stage 75 passes downwardly throughan opening or openings in the last intermediate permeable 85 d barrierlocated immediately below the intermediate permeable barrier 85.

In accordance with an exemplary embodiment as shown in the FIG. 1including five stages, an initial stream of oxygen-containing gas ispassed upwardly through the last stage 78 in counter-current contactwith the last stream of coked catalyst descending from a lastintermediate stage 95 to combust coke from the last stream of cokedcatalyst. In an embodiment, the initial stream has encountered verylittle coked catalyst because the last stage 78 is just above thedistributor 64. However, the coke concentration on the catalyst in thelast stream of coked catalyst in the last stage 78 is very low, muchlower than the coke concentration in the stream of coked catalyst in theupper first stage 70 and intermediate stages 75, because the last streamof coked catalyst has encountered more oxygen in more stages ofcounter-current contacting. Hence, a differential driving force ismaintained to drive combustion of the smaller concentration of cokedeposits in the last stream of coked catalyst with the largerconcentration of oxygen in the initial stream of oxygen-containing gas.The counter-current contacting may occur in the last section 98 topolish off any remaining coke deposits on the catalyst.

The counter-current contacting of the last stream of coked catalyst andthe initial stream of oxygen-containing gas combusts coke from thecatalyst to produce regenerated catalyst stream with a reducedconcentration of coke deposits and an intermediate stream ofoxygen-containing gas including flue gas. This regenerated catalyststream may have very little coke and be considered fully regeneratedcatalyst. However, in some embodiments, the regenerated catalyst streammay be partially regenerated catalyst. The intermediate stream ofoxygen-containing gas from the last stage is passed through the lastintermediate permeable barrier 85 d into the last intermediate stage.The catalyst in the last stage 78 is inhibited from upward movement bythe last intermediate permeable barrier 85 d and loses its momentum.Consequently, the regenerated catalyst stream of coked catalyst movesdownwardly through an opening or openings in the last permeable barrier100 from the last stage 78 in opposite direction to the upwardly flowinginitial stream of oxygen-containing gas. The regenerated catalyst streampasses through the last permeable barrier 100 past the distributor 64 toa regenerator riser 102, as discussed in detail below.

Because in the counter-current contacting of coked catalyst and primarystream of oxygen-containing gas, the oxygen-containing gas is introducedbelow the stages 70, 75 and 78, oxygen in the stage is consumed. We havefound that the ratio of carbon dioxide to carbon monoxide maximizes inthe intermediate stages 75. In stages that are higher in the regeneratorbut with a lower stage number, less oxygen is available, consequently, aratio of carbon dioxide to carbon monoxide is lower in the first stage70 than in the intermediate stages 75. Moreover, in the lowerintermediates stages 75 and the final stage 78 where coke is lessavailable, the ratio of carbon dioxide to carbon monoxide is lower. Forexample, the ratio of carbon dioxide to carbon monoxide is lower in thefinal stage 78 than in the intermediate stages 75 and even than in theinitial stage 70. Most importantly, the ratio of carbon dioxide tocarbon monoxide is smaller in the first stage than in the lower stagesand typically all stages with the exception of the last stage 78 inwhich sufficient residence time may not be available for carbon monoxideto oxidize to carbon dioxide despite the great availability of oxygen.Nevertheless, the first flue gas exiting the first stage 70 will have ahigher concentration of carbon monoxide which can be recovered in a COboiler with less risk of after burn because the concentration of oxygenin the flue gas is lower in the higher stages with the lower stagenumbers.

A portion of the primary stream of oxygen-containing gas may be divertedand fed to one of the stages 70, 75 and 78 separately (not shown) and/ora portion of a flue gas stream containing oxygen gas from a subjacentstage 75, 78 may be diverted to a superjacent stage 70, 75 to boost theoxygen concentration in the stage.

Although not shown in the Figures, catalyst coolers may be used ifneeded to cool a stream of coked catalyst such as by indirect heatexchange with liquid water to make steam. The cooled catalyst may betaken from and delivered to one of the stages 70, 75 and 78, preferablyat or below the first stage 70. In another example, a stream of cokedcatalyst can be taken from a stage at or below the first stage 70,cooled and returned to the intermediate stage or below the stage fromwhich it was taken. A catalyst cooler that withdraws catalyst from astage 70, 75 or 78, cools it and returns the cooled catalyst to the sameor subjacent stage is preferable.

In an embodiment, the regenerated catalyst obtained aftercounter-current regeneration below the last stage of the one or morestages may be passed from the regeneration section 54 to a bottom of theregenerator riser 102. The regenerator riser 102 preferably may have avertical orientation within the regenerator vessel 50 and may extendupwardly from the bottom of the regenerator vessel 50 through an axialcenter of the regenerator vessel 50 although other orientations are alsopossible. The regeneration section 54 may comprise an outlet for passingthe regenerated catalyst from the regeneration section 54 to the bottomof the regenerator riser 102. In accordance with an exemplary embodimentas shown in the FIG. 1, the regeneration section 54 may include aregeneration section outlet 106 in the bottom of the regenerationsection 54. In an embodiment, the regeneration section outlet mayinclude a first outlet 106 a and a second outlet 106 b. In accordancewith an exemplary embodiment as shown in the FIG. 1, the bottom of theregenerator riser 102 is located below the regeneration section 54 andmay include an inlet 104. In an embodiment, the bottom of theregeneration section may include a first inlet 104 a and a second inlet104 b. In accordance with an exemplary embodiment as shown in FIG. 1,the bottom of the regenerator riser 102 may be in communication with theregeneration section outlet 106 via a regenerator riser conduit 108extending from the regeneration section outlet to the inlet of theregenerator riser 102. In an embodiment, the bottom of the regeneratorriser 102 may be in communication with the regeneration section outlet106 via a first regenerator riser conduit 108 a and a second regeneratorriser conduit 108 b. In accordance with an exemplary embodiment as shownin the FIG. 1, the first inlet 104 a and the second inlet 104 b of theregenerator riser 102 are in communication with the regeneration section54 via the first regenerator riser conduit 108 a and the secondregenerator riser conduit 108 b, respectively. Subsequently, theregenerated catalyst is propelled via a secondary stream of gas to movethe regenerated catalyst from the bottom to a top of the regeneratorriser 102. In accordance with an exemplary embodiment as shown in theFIG. 1, the regenerator riser 102 may be located and passes throughinside of the vessel 50. The secondary stream of gas may be introducedthrough a secondary gas distributor 110. In an embodiment, the secondarystream of gas may be an oxygen containing gas. In accordance in anexemplary embodiment as shown in the FIG. 1, the secondary stream of gasmay be provided by the combustion gas in line 62.

In an embodiment, where partially regenerated catalyst is obtaineddownstream of the one or more stages, coke on the partially regeneratedcatalyst provided to the bottom of the regenerator riser is combusted asthe catalyst is propelled upwardly through the regenerator riser 102 toprovide a completely regenerated catalyst at the top of the regeneratorriser. The completely regenerated catalyst may be discharged from anoutlet 114 at the top of the regenerator riser 102. The regeneratorriser comprises a disengager 112 comprising the outlet 114 fordischarging the regenerated catalyst. The outlet 114 may be positionedin or above the upper surface of the fluidized bed to receive flue gasesand catalyst and initially separate catalyst from a second flue gasgenerated in the regenerator riser. In an aspect, heavier catalyst goesdown and lighter gas goes up after exiting the outlet 114 of thedisengager 112 to effect a rough separation. The second flue gas may bethe flue gas generated via combustion of coke from the catalyst in theregenerator riser 102. The CO₂-to-CO mole ratio for the second flue gasfrom the regenerator riser may be between about 3 to about 5. Theregenerated catalyst collects in the fluidized catalyst bed in theseparation section 56 and may be passed from a regenerated catalystoutlet 116 to the riser reactor 20 through the regenerated catalyststandpipe 12. In an embodiment, a fluffing fluidizing gas may beprovided to the separation section 56 to remove entrained flue gas fromthe catalyst and to fluidize catalyst to facilitate its removal from theseparation section 56. In an aspect, the fluffing fluidizing gas may beprovided by the first flue gas from the first stage 90 passing throughthe one or more vent tubes 109 from the regeneration section 54 into thecatalyst bed in the separation section 56.

The flue gas including the first flue gas generated in the regenerationsection 54 and the second flue gas from the regenerator riser 102 willusually contain a light loading of catalyst particles and may ascend inthe separation section 56. The flue gas consisting primarily of N₂, H₂O,O₂, CO₂ and traces of NO_(x), CO, and SO_(x) passes upwardly from thedense bed into a dilute phase of the regeneration vessel 50. Thecatalyst may be disengaged from flue gas which can then be dischargedfrom a flue gas outlet above all the stages 70, 75 and 78 including thefirst stage 70. The separation section 56 will contain a dilute phase ofcatalyst above the catalyst bed with catalyst entrained in the ascendingflue gas stream. In accordance with an exemplary embodiment as shown inthe FIG. 1, the flue gas may be processed through a separation devicesuch as a regenerator cyclone 118 to further separate catalyst from fluegas. The regenerator cyclone 118 or other means removes entrainedcatalyst particles from the rising flue gas and a dip leg 120 mayrelease catalyst which may be distributed on or near a top of thecatalyst bed in the separation section 56.

For partial burn conditions, the carbon monoxide concentration in theflue gas may be maintained at least at about 200 ppm and preferably atleast about 3 mole %, the CO₂-to-CO mole ratio may be between about 0.5to about 4.0, and preferably no more than about 0.9 and at least about0.5 and preferably at least about 0.8 and the oxygen concentration inthe flue gas stream exiting the first stage 70 may be less than about0.4 mole % and preferably no greater than about 0.2 mole %. For fullburn conditions, the carbon monoxide concentration in the flue gas maybe maintained at less than about 200 ppm, the CO₂-to-CO mole ratio maybe at least about 1.0 and the oxygen concentration in the flue gasstream exiting the first stage 70 may be greater than about 0.4 mole %.Further, oxygen concentration for partial burn conditions may be betweenabout 1000 pppw and about 0 pppw, wherein 0 ppmw signifies lowestdetectable value of the oxygen concentration in the flue gas. For fullburn conditions, the oxygen concentration would be greater than about5000 ppm and no greater than about 5 wt %.

If air is the oxygen-containing gas, typically 10 to 12 kg (lbs) of airare required per kg (lb) of coke fed on catalyst to the regeneratorvessel 50. The regenerator vessel 50 typically has a temperature ofabout 594 (1100° F.) to about 760° C. (1400° F.) and preferably about649 (1200° F.) to about 704° C. (1300° F.). Pressure may be between 173kPa (gauge) (25 psig) and 414 kPa (gauge) (60 psig). The superficialvelocity of the oxygen-containing gas through the stages 70, 75 and 78is typically between about 0.3 m/s (1 ft/s) and about 1.2 m/s (4.0ft/s), and the density of the catalyst in the stages 70, 75 and 78 istypically between about 400 kg/m³ (25 lb/ft³) and about 750 kg/m³ (47lb/ft³). The density of the flue gas in the dilute phase in theseparation section 56 is typically between about 4.8 kg/m³ (0.3 lb/ft³)and about 32 kg/m³ (2 lb/ft³) depending on the characteristics of thecatalyst with a superficial velocity of between about 0.6 m/s (2.0 ft/s)and about 1 m/s (3.0 ft/s).

Depending on the size and throughput of a regenerator vessel 50, betweenabout 4 and 60 regenerator cyclones 118 may be arranged in theseparation section 64. Flue gas may enter a plenum 122, usually near thetop of the separation section 56 before exiting through the flue gasoutlet 124.

Turning now to FIG. 2, another FCC unit is addressed with reference to aprocess and apparatus 400. Many of the elements in FIG. 2 have the sameconfiguration as in FIG. 2 and bear the same respective reference numberand have similar operating conditions. Elements in FIG. 2 thatcorrespond to elements in FIG. 1 but have a different configuration bearthe same reference numeral as in FIG. 2 but are marked with a primesymbol (′). The apparatus and process in FIG. 2 are the same as in FIG.1 with the exception of the noted following differences. In accordancewith the exemplary embodiment as shown in the FIG. 2, the regeneratorvessel 50 may further include a regenerated catalyst inlet 202 forreceiving a portion of the regenerated catalyst downstream of the one ormore stages in the regeneration vessel 50. The portion of theregenerated catalyst may be passed from an auxiliary regenerator vesseloutlet 204 in the regeneration section 54 of the regeneration vessel 50.In accordance with an exemplary embodiment as shown in the FIG. 2, theregenerated catalyst may be passed to the regenerator riser 102 througha regenerator riser conduit 206 extending from a bottom of theregeneration vessel 50 to the regenerated catalyst inlet 202 of theregenerator riser 102. In such an aspect, relatively cool spent catalystfrom the reactor section 10 and hot regenerated catalyst from theregeneration vessel 50 may be mixed and provided to the bottom of theregenerator riser 102. Accordingly, in accordance with an exemplaryembodiment as shown in FIG. 2, the portion of the regenerated catalystand the coked catalyst provide by the reactor section 10 may be mixed topreheat the coked catalyst, and the mixture of the regenerated catalystportion and the coked catalyst may be propelled from the bottom to thetop of the regenerator riser 102 via the secondary stream of gas andsubsequently processed as described in FIG. 1.

Turning now to FIG. 3, another FCC unit is addressed with reference to aprocess and apparatus 500. Many of the elements in FIG. 3 have the sameconfiguration as in FIG. 1 and bear the same respective reference numberand have similar operating conditions. Elements in FIG. 3 thatcorrespond to elements in FIG. 1 but have a different configuration bearthe same reference numeral as in FIG. 1 but are marked with a doubleprime symbol (″). The apparatus and process in FIG. 3 are the same as inFIG. 1 with the exception of the noted following differences. Inaccordance with the exemplary embodiment as shown in the FIG. 3, theregeneration section 54 and the separation section 56 are separated by awall 302 that is sealed to the wall 53 of the regenerator vessel 50. Inthe instant embodiment, the regeneration section 54 and separationsection 56 may be the regeneration chamber 54 and the separation chamber56, respectively. As shown in the FIG. 3, the regeneration section 54 isa fluid tight containment vessel except through one or more windows 304.The windows 304 may permit the passage of catalyst from the separationsection 56 to the regeneration section 54. The disengager 112 dischargesa mixture of the second flue gas and solid particles comprisingcatalyst. In an aspect, heavier catalyst goes down and lighter gas goesup after exiting the outlet 114 of the disengager 112 to effect a roughseparation. Catalyst from the outlet 114 collects in the fluidizedcatalyst bed in the regeneration section 54. In an embodiment, afluffing fluidizing gas may be provided in line 67 to the separationsection 56 to remove entrained flue gas from the catalyst and tofluidize catalyst to facilitate its removal from the separation section56. In accordance with an exemplary embodiment as shown in the FIG. 3,the fluffing fluidizing gas may be provided by a fluffing gas ringdistributor 312.

The flue gas comprising the first flue gas from the one or more stagesand the second flue gas from the regenerator riser, begin an upwardspiral with the gases ultimately traveling into a gas recovery conduit306 having an inlet 308 that serves as the gas outlet for regenerationsection 54. The flue gas that enters the gas recovery conduit 306through the inlet 308 will usually contain a light loading of catalystparticles. In accordance with an exemplary embodiment as shown in FIG.3, the gas recovery conduit 306 may pass the flue gas to a separationdevice such as regenerator cyclones 118 to further separate catalystfrom flue gas. In accordance with an exemplary embodiment as shown inthe FIG. 3, ducts 310 may connect regenerator cyclones 118 to the gasrecovery conduit 306 and may provide the passage for passing the fluegas directly to the regenerator cyclones 118. The regenerator cyclones118 or other means removes entrained catalyst particles from the risingflue gas, and a dip leg 120 may release catalyst to the catalyst bed inthe separation section 56 from the respective cyclone 118.

Depending on the size and throughput of a regenerator vessel 50, betweenabout 4 and 60 regenerator of the regenerator cyclones 118 may bearranged in the separation section 64. Flue gas from the regeneratorcyclones 118 may enter a plenum 122, usually near the top of theseparation section 56 before exiting through the flue gas outlet 124.

Specific Embodiments

While the following is described in conjunction with specificembodiments, it will be understood that this description is intended toillustrate and not limit the scope of the preceding description and theappended claims.

A first embodiment of the invention is a process for combusting cokefrom coked catalyst in a regenerator vessel, the process comprising a)providing a coked catalyst to an inlet in a bottom of a regeneratorriser; b) propelling the coked catalyst upwardly from the bottom of theregenerator riser to a top of the regenerator riser via a secondarystream of gas; c) discharging catalyst from an outlet in the top of theregenerator riser; d) passing the catalyst downwardly through a one ormore stages, each of the one or more stages comprising a permeablebarrier; e) passing a primary stream of oxygen-containing gas upwardlythrough the one or more stages in counter-current contact with thecatalyst to combust coke from the coked catalyst to provide aregenerated catalyst and a flue gas; and f) passing the regeneratedcatalyst from a regenerated catalyst outlet to a riser reactor through aregenerated catalyst standpipe. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the fourthembodiment in this paragraph, wherein the step of propelling the cokedcatalyst upwardly from the bottom of the regenerator riser provides apartially regenerated catalyst via combustion of the coked catalyst. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the fourth embodiment in this paragraph,wherein the step of passing the primary stream of oxygen-containing gasin counter-current contact with the coked catalyst provides a completelyregenerated catalyst via combustion of coke from the partiallyregenerated catalyst. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the fourth embodimentin this paragraph further comprising passing a portion of the completelyregenerated catalyst to the bottom of the regenerator riser via aregenerator riser conduit extending from the bottom of the regenerationvessel. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the fourth embodiment in thisparagraph, wherein the permeable barrier inhibits upward movement of thecoked catalyst. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the fourth embodiment inthis paragraph, wherein passing the catalyst downwardly through the oneor more stages comprising permeable barriers comprises passing a firststream of coked catalyst downwardly through a first permeable barrierinto a first stage; passing a first stream of oxygen-containing gasupwardly through the first stage in counter-current contact with thefirst stream of coked catalyst to combust coke from the first stream ofcoked catalyst to provide a second stream of coked catalyst includingregenerated catalyst and a stream of flue gas; passing the stream offlue gas upwardly from the first stage; inhibiting upward movement ofthe first stream of coked catalyst in the first stage by the firstpermeable barrier; passing the second stream of coked catalystdownwardly from the first stage to a second stage below the first stage;passing a second stream of oxygen-containing gas upwardly through thesecond stage in counter-current contact with the second stream of cokedcatalyst to combust coke from the second stream of coked catalyst toprovide a third stream of coked catalyst including regenerated catalystand the first stream of oxygen-containing gas including flue gas;passing the first stream of oxygen-containing gas from the second stageto the first stage; and inhibiting upward movement of the second streamof coked catalyst in the second stage via a second permeable barrier. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the fourth embodiment in this paragraphfurther comprising passing the third stream of coked catalyst downwardlyfrom the second stage to a third stage below the second stage; passing athird stream of oxygen-containing gas upwardly through the third stagein counter-current contact with the stream of coked catalyst to combustcoke from the coked catalyst to provide a fourth stream of cokedcatalyst comprising regenerated catalyst and the second stream ofoxygen-containing gas including flue gas; and inhibiting upward movementof the third stream of coked catalyst in the third stage. An embodimentof the invention is one, any or all of prior embodiments in thisparagraph up through the fourth embodiment in this paragraph, whereinthe regeneration vessel comprises a regeneration section and aseparation section, the regeneration section located below theseparation section and separated by a wall. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the fourth embodiment in this paragraph, wherein theregeneration section is a fluid tight containment vessel with one orwindows to permit the passage of catalyst from the separation section tothe regeneration section.

A second embodiment of the invention is a process for combusting cokefrom coked catalyst in a regenerator vessel, the process comprisingproviding a coked catalyst to an inlet in a bottom of a regeneratorriser; propelling the coked catalyst upwardly from the bottom of theregenerator riser to a top of the regenerator riser via a secondarystream of oxygen-containing gas to provide a partially regeneratedcatalyst via combustion of the coked catalyst; discharging the partiallyregenerated catalyst from an outlet in the top of the regenerator riser;passing the partially regenerated catalyst downwardly through a one ormore stages, each of the one or more stages comprising a permeablebarrier; passing a primary stream of oxygen-containing gas upwardlythrough the one or more stages in counter-current contact with thepartially regenerated catalyst to combust coke from the partiallyregenerated catalyst to provide a completely regenerated catalyst and aflue gas; and passing the completely regenerated catalyst from aregenerated catalyst outlet in a bottom of the regeneration vessel to ariser reactor through a regenerated catalyst standpipe.

A third embodiment of the invention is an apparatus for combusting cokefrom coked catalyst, the regenerator vessel comprising (a) a regeneratorriser comprising (i) an inlet in a bottom of the regenerator riser indownstream communication with a spent catalyst standpipe for feedingcoked catalyst; and (ii) an outlet for discharging catalyst from theregenerator riser; (b) a one or more stages located above the inlet ofthe regenerator riser and below the outlet of the regenerator riser,each of the one or more stages comprising a permeable barrier comprisingopenings sized to permit the catalyst to pass through downwardly, thepermeable barriers extending laterally across the regenerator vessel;(c) a combustion gas distributor for passing a primary stream ofoxygen-containing gas upwardly through the one or more stages incounter-current contact with the catalyst to combust coke from the cokedcatalyst to provide a regenerated catalyst and a flue gas; (d) aregenerated catalyst outlet, the regenerated catalyst outlet locatedbelow the one or more stages; (e) one or more cyclone separators forseparating catalyst from the flue gas; and (f) a flue gas outlet in theregenerator vessel. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the sixth embodiment inthis paragraph, wherein the regenerator vessel comprises a regenerationsection and a separation section, the regeneration section located belowthe separation section and separated by a wall. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the sixth embodiment in this paragraph, wherein the regenerationsection is a fluid tight containment vessel with one or windows topermit the passage of catalyst from the separation section to theregeneration section. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the sixth embodimentin this paragraph, wherein one or more stages are present in theregeneration section. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the sixth embodimentin this paragraph, wherein the outlet of the regenerator riser islocated in the separation section above the one or more stages. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the sixth embodiment in this paragraph,wherein the inlet of the regenerator riser is located below theregeneration vessel. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the sixth embodimentin this paragraph, wherein the inlet is a spent catalyst inlet and theregenerator riser further comprises a regenerated catalyst inlet incommunication with the regeneration vessel via a regenerator riserconduit extending from the regeneration vessel to the regeneratedcatalyst inlet of the regenerator riser. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thesixth embodiment in this paragraph, wherein regeneration vesselcomprises at least two stages comprising a first permeable barrier belowthe catalyst inlet, the first permeable barrier extending laterallyacross the regenerator vessel; a second permeable barrier below thefirst permeable barrier to define a second stage, the second permeablebarrier extending laterally across the regenerator vessel; and theregeneration catalyst outlet below the second permeable barrier. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the sixth embodiment in this paragraph whereinthe second permeable barrier is spaced below the first permeablebarrier. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the sixth embodiment in thisparagraph further comprising a third permeable barrier below the secondpermeable barrier and above the regenerator catalyst outlet, the thirdpermeable barrier extending laterally across the regenerator vessel.

Without further elaboration, it is believed that using the precedingdescription that one skilled in the art can utilize the presentinvention to its fullest extent and easily ascertain the essentialcharacteristics of this invention, without departing from the spirit andscope thereof, to make various changes and modifications of theinvention and to adapt it to various usages and conditions. Thepreceding preferred specific embodiments are, therefore, to be construedas merely illustrative, and not limiting the remainder of the disclosurein any way whatsoever, and that it is intended to cover variousmodifications and equivalent arrangements included within the scope ofthe appended claims.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

The invention claimed is:
 1. A regenerator vessel for combusting cokefrom coked catalyst, the regenerator vessel comprising: (a) aregeneration section and a separation section, the regeneration sectionis a fluid tight containment vessel having one or more windows to permitthe passage of the coked catalyst from the separation section to theregeneration section; (b) a regenerator riser comprising: (i) an inletin a bottom of the regenerator riser in downstream communication with aspent catalyst standpipe for feeding the coked catalyst; and (ii) anoutlet for discharging catalyst from the regenerator riser; (c) a one ormore stages located above the inlet of the regenerator riser and belowthe outlet of the regenerator riser, each of the one or more stagescomprising a permeable barrier comprising openings sized to permit thecatalyst to pass through downwardly, the permeable barriers extendinglaterally across the regenerator vessel; (d) a combustion gasdistributor for passing a primary stream of oxygen-containing gasupwardly through the one or more stages in counter-current contact withthe catalyst to combust coke from the coked catalyst to provide aregenerated catalyst and a flue gas; (e) a regenerated catalyst outlet,the regenerated catalyst outlet located below the one or more stages;(f) one or more cyclone separators for separating catalyst from the fluegas; and (g) a flue gas outlet in the regenerator vessel.
 2. Theregenerator vessel of claim 1, wherein the regeneration section locatedbelow the separation section and separated by a wall.
 3. The regeneratorvessel of claim 1, wherein one or more stages are present in theregeneration section.
 4. The regenerator vessel of claim 1, wherein theoutlet of the regenerator riser is located in the separation sectionabove the one or more stages.
 5. The regenerator vessel of claim 1,wherein the inlet of the regenerator riser is located below theregeneration vessel.
 6. The regenerator vessel of claim 1, wherein theinlet is a spent catalyst inlet and the regenerator riser furthercomprises a regenerated catalyst inlet in communication with theregeneration vessel via a regenerator riser conduit extending from theregeneration vessel to the regenerated catalyst inlet of the regeneratorriser.
 7. The regenerator vessel of claim 1, wherein regeneration vesselcomprises at least two stages comprising: a first permeable barrierbelow the outlet, the first permeable barrier extending laterally acrossthe regenerator vessel; a second permeable barrier below the firstpermeable barrier to define a second stage, the second permeable barrierextending laterally across the regenerator vessel; and the regenerationcatalyst outlet below the second permeable barrier.
 8. The regeneratorvessel of claim 7 wherein the second permeable barrier is spaced belowthe first permeable barrier.
 9. The regenerator vessel of claim 7further comprising a third permeable barrier below the second permeablebarrier and above the regenerator catalyst outlet, the third permeablebarrier extending laterally across the regenerator vessel.
 10. Aregenerator vessel for combusting coke from coked catalyst, theregenerator vessel comprising: (a) a regenerator riser extendingupwardly through the regenerator vessel comprising: (i) an inlet in abottom of the regenerator riser in downstream communication with a spentcatalyst standpipe for feeding the coked catalyst; and (ii) an outletfor discharging catalyst from the regenerator riser; (b) a one or morestages located above the inlet of the regenerator riser and below theoutlet of the regenerator riser, each of the one or more stagescomprising a permeable barrier comprising openings sized to permit thecatalyst to pass through downwardly, the permeable barriers extendinglaterally across the regenerator vessel; (c) a combustion gasdistributor for passing a primary stream of oxygen-containing gasupwardly through the one or more stages in counter-current contact withthe catalyst to combust coke from the coked catalyst to provide aregenerated catalyst and a flue gas; (d) a regenerated catalyst outlet,the regenerated catalyst outlet located below the one or more stages;(e) one or more cyclone separators for separating catalyst from the fluegas; and (f) a flue gas outlet in the regenerator vessel.
 11. Theregenerator vessel of claim 10, wherein the regenerator vessel comprisesa regeneration section and a separation section, the regenerationsection located below the separation section and separated by a wall.12. The regenerator vessel of claim 11, wherein the regeneration sectionis a fluid tight containment vessel with one or windows to permit thepassage of catalyst from the separation section to the regenerationsection.
 13. The regenerator vessel of claim 10, wherein one or morestages are present in the regeneration section.
 14. The regeneratorvessel of claim 10, wherein the outlet of the regenerator riser islocated in the separation section above the one or more stages.
 15. Theregenerator vessel of claim 10, wherein the inlet of the regeneratorriser is located below the regeneration vessel.
 16. The regeneratorvessel of claim 10, wherein the inlet is a spent catalyst inlet and theregenerator riser further comprises a regenerated catalyst inlet incommunication with the regeneration vessel via a regenerator riserconduit extending from the regeneration vessel to the regeneratedcatalyst inlet of the regenerator riser.
 17. The regenerator vessel ofclaim 10, wherein regeneration vessel comprises at least two stagescomprising: a first permeable barrier below the catalyst inlet, thefirst permeable barrier extending laterally across the regeneratorvessel; a second permeable barrier below the first permeable barrier todefine a second stage, the second permeable barrier extending laterallyacross the regenerator vessel; and the regeneration catalyst outletbelow the second permeable barrier.
 18. The regenerator vessel of claim17 wherein the second permeable barrier is spaced below the firstpermeable barrier.
 19. The regenerator vessel of claim 17 furthercomprising a third permeable barrier below the second permeable barrierand above the regenerator catalyst outlet, the third permeable barrierextending laterally across the regenerator vessel.